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Merge pull request #895 from iconexperience/further-simplify-winding-calculation2

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Further simplify and explain winding calculation in getWinding() (2)
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Jürg Lehni 2016-01-08 10:00:55 +01:00
commit 18e00f6312
1 changed files with 32 additions and 25 deletions
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47
src/path/PathItem.Boolean.js
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@ -357,7 +357,7 @@ PathItem.inject(new function() {
// the last non-horizontal curve, which will be the previous // the last non-horizontal curve, which will be the previous
// non-horizontal curve for the first curve of the loop. // non-horizontal curve for the first curve of the loop.
prevWinding = last.winding, prevWinding = last.winding,
prevEnd = last.values[6]; prevXEnd = last.values[6];
end = start + curve.length; end = start + curve.length;
for (var i = start; i < end; i++) { for (var i = start; i < end; i++) {
var curve = curves[i], var curve = curves[i],
@ -369,37 +369,44 @@ PathItem.inject(new function() {
// compare the endpoints of the curve to determine if the // compare the endpoints of the curve to determine if the
// ray from query point along +-x direction will intersect // ray from query point along +-x direction will intersect
// the monotone curve. // the monotone curve.
// horizontal curves with winding == 0 will be completely
// ignored
if (winding && (py >= yStart && py <= yEnd if (winding && (py >= yStart && py <= yEnd
|| py >= yEnd && py <= yStart)) { || py >= yEnd && py <= yStart)) {
// calculate the x value for the ray's intersection
var x;
if (py === yStart) { if (py === yStart) {
var x = values[0]; x = values[0];
if (winding * prevWinding < 0) { } else if (py === yEnd) {
if (x > xBefore && x < xAfter) { x = values[6];
++windLeft; } else if (Curve.solveCubic(values, 1, py, roots, 0, 1) === 1) {
++windRight; x = Curve.getPoint(values, roots[0]).x;
} else if (x < xBefore) {
windLeft += winding;
} else if (x > xAfter) {
windRight += winding;
} }
} else if (x < xBefore && prevEnd > xBefore) { if (x != null) {
windLeft += winding; // count the intersection of the ray with the monotonic curve if
} else if (x > xAfter && prevEnd < xAfter) { // - the crossing is not at the start of the curve
windRight += winding; // - or the windings are opposite (intersect at a vertical extremum)
} // - or the start of the current curve and the end of the prev
} else if (Curve.solveCubic(values, 1, py, roots, 0, 1) // curve are on opposite sides of px
=== 1) { var isWindingChange = winding === -prevWinding,
var x = Curve.getPoint(values, roots[0]).x; countIntersection = py !== yStart || isWindingChange ||
(x - px) * (prevXEnd - px) < 0;
if (countIntersection) {
if (x < xBefore) { if (x < xBefore) {
windLeft += winding; windLeft += winding;
} else if (x > xAfter) { } else if (x > xAfter) {
windRight += winding; windRight += winding;
} else if (py === yStart && isWindingChange) {
// intersection is at a vertical extremum
++windLeft;
++windRight;
}
} }
} }
// Update previous winding and end coordinate whenever // Update previous winding and end coordinate whenever
// we encountered a non-horizontal curve. // the ray intersects a non-horizontal curve.
prevWinding = winding; prevWinding = winding;
prevEnd = values[6]; prevXEnd = values[6];
} }
} }
} }